I'd like to suggest AeroSQL, it's an open source (GPL) web based MySql Manager built using PHP and ExtJS library.
There is a demo, video and screenshots available.
Project homepage: http://www.burlaca.com/aerosql/
The key feature of the product is an intuitive management of the database content. The result of SELECTs is displayed in a grid as in traditional desktop applications. The grid is editable: you can update cells and save the changes to the backend database server.